A number of different types of plate shifters have been devised in an attempt to facilitate the shifting of filter plates as used in filter presses. Such plate shifter have typically involved mechanisms which are complex and subject to failure when, for example, the filter press becomes dirty due to sludge or other contaminating materials accumulating thereon.
One conventional type of plate shifter mechanism involves a support carriage which is movable longitudinally along the filter press frame and mounts thereon a pair of pawls which are designed for cooperation with opposite sides of the individual plates to effect shifting thereof. In such mechanism, the two shifting pawls generally operate wholly independently of one another, and are each individually spring biased into an upper position, whereby they are configured to cooperate with the filter plates to perform the desired shifting function. Such arrangement, an example of which is illustrated by U.S. Pat. No. 3 306 455, introduces greater operational and structural complexity inasmuch as each shifting pawl is pivotal independently of the other and is independently spring urged, thereby not only increasing the structural complexity but also increasing the possibility of failure or malfunction due to the independent relationship between the pawls.
Accordingly, this invention relates to an improved plate-shifter mechanism employing a pair of movable shifter pawls, only one of which is spring biased, which pawls structurally and functionally cooperate with one another during the plate-shifting function so as to result in a mechanism having increased structural and operational simplicity and dependability.
More specifically, the improved plate-shifter mechanism of this invention includes a support carriage which is movable in a linear reciprocal manner in the lengthwise direction of the filter press. This support carriage mounts thereon, in longitudinally spaced relation, a pair of pivotal shifting pawls disposed in opposed relationship. The pawls, in the vicinity of the free ends, have upper cam surfaces which functionally cooperate with the sidewardly-projecting drive lugs associated with the filter plates. The first shifting pawl is spring urged upwardly toward the drive lugs, whereas the second shifting pawl is free of springs. This second shifting pawl, adjacent the free end thereof, is provided with a projecting nose part which projects into a clearance slot formed adjacent the free end of the first pawl, whereby the second pawl is free to move either independently of the first pawl or in controlled synchronous movement with the first pawl.
Other objects and purposes of the invention will be apparent to persons familiar with structures of this general type upon reading the following specification and inspecting the accompanying drawings.